Catalytic process for oxidation of carbon monoxide

ABSTRACT

In a process for preparing a reduced material comprising (a) alumina and/or magnesium aluminate as support material, (b) platinum metal and (c) an iron component, the improvement comprises: (1) treating the reduced composition of matter with an acidic liquid; (2) heating the acid-treated material, and (3) treating the material obtained in step (2) with a reduced gas. The prepared material is used as a catalyst for converting CO and O 2  to CO 2 .

This is a division of patent application Ser. No. 07/366,946, filed June14, 1989, now U.S. Pat. No. 4,943,550.

BACKGROUND OF THE INVENTION

This invention relates to the catalytic oxidation of carbon monoxide. Inanother aspect, this invention relates to effective CO oxidationcatalyst compositions. In still another aspect, this invention relatesto a process for preparing CO oxidation catalyst compositions.

The use of catalysts for the oxidation of carbon monoxide to carbondioxide by reaction with oxygen, in particular at low temperature, is ofmuch interest, e.g., in breathing masks designed to remove CO frominhaled air, in tobacco products so as to minimize CO in tobacco smoke,and in CO₂ lasers so as to recombine CO and O₂ formed by dissociation ofCO₂ during discharge. In the latter application, the presence of O₂ ismost undesirable because it can cause a breakdown of the electricalfield in the laser cavity. Several patents, e.g., U.S. Pat. No.4,639,432, disclose compositions useful as CO oxidation catalysts in CO₂laser applications. A particularly effective CO oxidation catalystcomposition is described in U.S. Pat. No. 4,818,745, the entiredisclosure of which is herein incorporated by reference. However, thereis an ever present need to develop new, effective CO oxidation catalystcompositions and/or improved processes for preparing effective COoxidation catalyst compositions.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a process for preparing acomposition of matter which is effective as a catalyst for the oxidationof carbon monoxide with free oxygen. It is another object of thisinvention to provide a composition of matter which is effective as a COoxidation catalyst. It is a further object of this invention to providean effective process for catalytically oxidizing carbon monoxide withfree oxygen. Other objects and advantages will be apparent from thedetailed description and the claims.

In accordance with this invention, in a process for preparing acomposition of matter (which is effective as a catalyst composition forthe reaction of carbon monoxide with free oxygen to carbon dioxide)comprising (preferably consisting essentially of) (a) a support materialselected from the group consisting of alumina, magnesium aluminate andmixtures thereof, (b) platinum metal, and (c) an iron component selectedfrom the group consisting of iron metal, iron oxides and mixtures(preferably iron oxide), wherein said composition of matter hasundergone a reducing treatment (preferably with H₂ and/or CO), theimprovement comprises:

(1) treating the composition of matter which has undergone a reducingtreatment with an acidic liquid (preferably an aqueous acid solution);

(2) heating the material obtained in step (1) under such conditions asto substantially remove said acidic liquid from said material obtainedin step (1); and

(3) treating the material obtained in step (2) with a reducing gas(preferably H₂ and/or CO) under such conditions as to enhance theactivity of said material for catalyzing the reaction of carbon monoxidewith free oxygen to carbon dioxide (in particular, when this reaction ofCO with O₂ is carried out at a temperature of about 10°-50° C.).

In one preferred embodiment, the acidic compound used in step (1) is anaqueous solution. In another preferred embodiment, heating step (2) iscarried out at a temperature high enough for a period of time longenough (more preferably at about 80°-700° C. for about 0.5-20 hours) tosubstantially decompose iron compounds which have been formed with theacidic liquid in step (1) to at least one iron oxide. In a furtherpreferred embodiment, the reducing treatment of step (3) is carried outat a temperature of at least about 20° C. for at least one minute (morepreferably at about 20°-600° C. for about 0.5-20 hours).

Also in accordance with this invention, a process for the oxidation ofcarbon monoxide with free oxygen to carbon dioxide employs as catalystthe above-described composition of matter having undergone steps (1),(2) and (3). Preferably, the CO oxidation process is carried out at atemperature below about 400° C. (more preferably at about -50° to about400° C.).

Further in accordance with this invention, a composition of matter isprovided having been prepared by the above-described preparation processcomprising steps (1), (2) and (3).

DETAILED DESCRIPTION OF THE INVENTION

Any alumina and/or magnesium aluminate can be used as the supportmaterial for the composition of matter of this invention. Presentlypreferred are substantially pure alumina (aluminum oxide) and/ormagnesium aluminate spinel. More preferably, the support materialcontains at least about 95 weight percent Al₂ O₃ or Mg aluminate. Thesesupport materials are commercially available.

The method of preparation of alumina is not considered critical.Generally, first hydroxides and/or hydrated oxides of aluminum areprecipitated from an aqueous solution of a dissolved aluminum compoundby means of a suitable alkaline substance (e.g., aqueous NH₃). Then theprecipitate is separated, washed, and finally heated so as to removewater therefrom and to convert aluminum hydroxide to aluminum oxide.

The preparation of magnesium aluminate spinel, having the approximatechemical formula of MgAl₂ O₄ is not considered critical. In a preferredembodiment, Mg aluminate is prepared by ball-milling alumina powder andmagnesia powder at an appropriate weight ratio, molding the mixture intoa desired shape (e.g., spherical), drying, and calcining (e.g., at about1350° C. for 10 hours), as has been described in Examples 1-5 of U.S.Pat. No. 4,239,656, the disclosure of which is herein incorporated byreference.

Generally the surface area (determined by the BET/N₂ method; ASTM D3037)of alumina and magnesium aluminate (or mixtures thereof) is in the rangeof from about 10 to about 350 m² /g. Alumina and/or Mg aluminate canhave spherical, cylindrical, trilobal, quadrilobal, ring-like orirregular shapes. When spheres are used, their diameter generally is inthe range of from about 0.2 to about 20 mm, preferably about 1-5 mm.

It is within the scope of this invention to prepare suitable supportmaterials by coating an inert porous ceramic material, such as amonolith (commercially available from Corning Glass Works, Corning,N.Y.; described in U.S. Pat. Nos. 4,388,277 and 4,524,051) with aluminaand/or Mg aluminate. The monolith can be impregnated with an organiccompound of Al (such as trialkyl Al), hydrolyzed, dried, and calcined toform alumina-coated monolith. Or the monolith can be impregnated with adispersion (preferably colloidal) of Al oxide/hydroxide, followed bydrying and calcining. When a magnesium aluminate-coated monolith is tobe formed, the monolith can be impregnated with organic compounds of Mgand Al or with a dispersion of oxides/hydroxides of Mg and Al, followedby drying and calcining at a temperature high enough to form Mgaluminate-coated monolith.

The impregnation of the support material with Pt and Fe can be carriedout in any suitable manner. Generally, compounds of Pt and of Fe aredissolved in a suitable solvent (preferably water) so as to preparesolutions of suitable concentration, generally containing from about0.005 to about 0.40 g Pt per cc solution and about 0.005 to about 0.40 gFe per cc of solution. Non-limiting examples of suitable Pt compoundsare nitrates or organic compounds of platinum, such as carboxylates oracetylacetonates of Pt, preferably Pt(NH₃)₄ (NO₃)₂. Non-limitingexamples of suitable Fe compounds are: Fe(NO₃)₂, Fe(NO₃)₃ (preferred),Fe carboxylates, Fe acetylacetonate, and the like. It is understood thatorganic solvents, such as methanol, ethanol, acetone, ethyl acetate,toluene and the like, can be used as solvents for organic compounds ofPt and Fe.

The support material is impregnated by soaking it in the solution of Ptand Fe compounds; or (less preferably) the Pt and Fe containing solutionis sprayed onto the support material. The ratio of Pt and Fe solution tosupport material generally is such that the final composition of matterof this invention contains about 0.1 to about 10 weight percent Pt,preferably about 0.5 to about 5 weight percent Pt, and about 0.05 toabout 20 weight percent Fe, preferably about 0.1 to about 4 weightpercent Fe. However, it is within the scope of this invention to havecomponents (b) and (c) present at any weight percentage such that (c)acts as a copromoter for (b) in the oxidation of CO with O₂, inparticular at about 10°-50° C. Even though it is presently preferred tosimultaneously impregnate the support material with dissolved compoundsof Pt and Fe, the impregnation (or spraying) of the support material canalso be carried out sequentially (first Fe, then Pt, or vice versa).

Heating of the Pt/Fe-impregnated material is generally carried out in aninert or oxidizing atmosphere, preferably a free oxygen containing gasatmosphere (such as air), generally at a temperature ranging from about80° to about 700° C. Preferably, heating is carried out in twosequential sub-steps: first at about 80° to about 200° C. (preferably atabout 80°-130° C.), generally for about 0.5 to about 10 hours, so as tosubstantially dry the Pt/Fe-impregnated material (preferably under suchconditions as to reduce the level of adhered and occluded water to lessthan about 10 weight percent); and then at about 250° to about 700° C.(preferably about 400° to about 600° C.), generally for about 0.5 toabout 10 hours, under such conditions as to substantially calcine theimpregnated support material so as to obtain at least one Pt oxide,optionally mixed with metallic Pt, and at least one Fe oxide on aluminaand/or Mg aluminate.

Reducing of the calcined, Pt/Fe-impregnated material can be carried outin any suitable manner, preferably at a temperature in the range of fromabout 20° to about 650° C., more preferably from about 200° to about500° C. Any reducing gas can be employed, such as a gas comprising H₂,CO, gaseous hydrocarbons such as methane, mixtures of the above, and thelike. Preferably, a free hydrogen containing gas, more preferably a gasstream of substantially pure H₂, is employed. The reducing step can becarried out for any suitable period of time, generally at least about 1minute, preferably from about 0.5 to about 20 hours, more preferablyabout 1-5 hours. During the reducing treatment, platinum oxide isgenerally substantially reduced to platinum metal; whereas, it isbelieved that either substantially no reduction of iron oxide to ironmetal occurs or that only a minor portion of iron oxide is reduced tometallic iron.

Step (1) of the improvement process of this invention can be carried outin any suitable manner. Any suitable inorganic or organic acid having apH of less than about 7 can be used in step (1). Preferably, an aqueoussolution of nitric acid or of a carboxylic acid (more preferably aceticacid) is used as acidic liquid. However, it is within the scope of thisinvention to use substantially water-free glacial acetic acid foracid-treatment step (1). Suitable concentrations for the two preferredacidic liquids are: about 0.01-15 mole/l of HNO₃ and about 0.1-18 mole/lof acetic acid. The previously reduced Pt/Fe-containing material(described above) is soaked in step (1) with the acidic liquid(generally at a temperature of about 10°-80° C.) for a suitable periodof time (generally for about 0.01-1 hour), preferably with sufficientliquid to attain incipient wetness (i.e., just enough liquid to fill allthe pores of the supported Pt/Fe oxide material).

Step (2) of the improvement process of this invention can be carried outby any suitable means which result in the substantial removal of theacid and solvent (in particular water) from the material obtained instep (1). Furthermore, in step (2) substantially all compounds of Fewhich have been formed by reaction of iron oxide or metal with the acidin step (1) are converted to iron oxide, i.e., one or a plurality ofoxides of Fe. In addition, in step (2) any platinum compounds which mayhave been formed in step (1) will be substantially decomposed toplatinum oxide, optionally admixed with Pt metal. Preferably, step (2)is carried out in an inert or oxidizing atmosphere, preferably a freeoxygen containing gas (such as air), generally at a temperature in therange of from about 80° to about 700° C. Preferably, step (2) is carriedout in two sequential sub-steps: first at about 80°-200° C. (preferablyabout 80°-130° C.) for about 0.3-10 hours, so as to substantially drythe material obtained in step (1), and thereafter heating thesubstantially dried material at about 250°-700° C. (preferably about400°-600° C.), generally for about 0.2-10 hours, so as to obtainplatinum oxides optionally admixed with Pt metal, and iron oxide onalumina and/or Mg aluminate support.

Reducing step (3) can be carried out in any suitable manner, preferablyat a temperature of about 20°-650° C. (more preferably about 200°-500°C.) for about 0.5-20 hours (preferably about 1-5 hours), so as toenhance the activity of the composition of matter for catalyzing lowtemperature CO oxidation with O₂, i.e., to enhance the conversion of COand O₂, to CO₂ in a test carried out at about 10°-50° C., as comparedwith the material obtained in step (2). In addition, the producedmaterial obtained in step (3) has a higher CO oxidation activity thanthe reduced material used as starting material in step (1). Any reducinggas can be used in step (3): H₂, CO, paraffins such as CH₄, and thelike, and mixtures thereof. Preferably, a stream comprising H₂ orpreferably a stream of substantially pure H₂, is employed in step (3).In reducing step (3), substantially all platinum oxide is reduced toplatinum metal; whereas, it is believed that either substantially noreduction of iron oxide to iron metal occurs (especially at relativelylow reducing temperatures) or that only a minor portion of iron oxide isreduced to iron metal (especially at higher reducing temperatures).Thus, substantially all or a major portion of the iron component remainsin the oxidic form in the final composition of matter of this invention.The material obtained in step (3) comprises, preferably consistsessentially of, components (a), (b) and (c), as defined above, at weightpercentages described above.

The process for oxidizing a carbon monoxide containing feed gas can becarried out at any suitable temperature and pressure conditions, for anysuitable length of time, at any suitable gas hourly space velocity, andany suitable volume ratio of CO and O₂. The reaction temperaturegenerally is in the range of from about -50° to about 400° C.,preferably from about -30° to about 170° C., more preferably from about10° to about 50° C. The pressure during the oxidation process generallyis in the range of from about 0.1 to about 2,000 psia, preferably fromabout 5 to about 20 psia. The volume ratio of CO to O₂ in the feed gascan range from about 1:100 to about 100:1, and preferably is in therange of from about 1:10 to about 10:1. The volume percentage of CO andthe volume percentage of O₂ in the feed gas can each be in the range offrom about 0.05 to about 50, preferably from about 0.05 to about 3. Thegas hourly space velocity (cc feed gas per cc catalyst per hour) can bein the range of from about 1 to about 200,000, preferably from about 100to about 50,000. It is understood that the calculation of the gas hourlyspace velocity is based on the volume of the active catalyst, i.e., thealumina and/or Mg aluminate supported Pt/Fe oxide catalyst, excludingthe volume occupied by any additional inert support material, such as amonolith, which may be present.

The feed gas can be formed in any suitable manner, e.g., by mixing CO,O₂ and, optionally, other gases such as CO₂, N₂, He and the like, suchas in a carbon dioxide laser cavity. The feed gas can be an exhaust gasfrom a combustion engine, or it can be contaminated air or smoke from acigarette (or cigar or pipe) that is to be inhaled by humans andcontains undesirably high levels of toxic carbon monoxide, and the like.The feed gas can be contacted in any suitable vessel or apparatus, suchas in a laser cavity, or in an exhaust pipe of a combustion engine, orin a gas mask (used by humans), or in a smoking article (cigarette,cigar, pipe), wherein the feed gas passes over the catalyst compositionof this invention at the conditions described above. The CO oxidationprocess of this invention can be carried out in any suitable setting andfor any purpose, e.g., to recombine CO and O₂ in CO₂ lasers, to oxidizeCO contained in exhaust gases or in air, to make isotopically labeledCO₂ from CO and the ₈ ¹⁸ O isotope, and the like.

The following examples are presented in further illustration of theinvention and are not to be construed as unduly limiting the scope ofthe invention.

EXAMPLE I

This example illustrates the preparation of various alumina-supportedPt/Fe catalysts and their evaluation for low temperature CO oxidationactivity.

A 5.5 gram sample of a commercial catalyst material (provided by GeneralMotors Corp., Detroit, Mich.) containing 0.1 weight percent Pt onalumina was sequentially impregnated several times with 7.8 grams of anaqueous solution of dissolved Pt(NH₃)₄ (NO₃)₂ and Fe(NO₃)₃ comprisingabout 0.02 g Pt/g solution and about 0.01 g Fe/g solution. Betweensuccessive impregnations, the material was dried at about 125° C. Theimpregnation was continued until the solid material contained about 3weight percent Pt and about 1.5 weight percent Fe. The thus-impregnatedmaterial was calcined in air at about 400° C. for about 3 hours. Thiscalcined material is labeled Catalyst A.

Catalyst B was prepared by reducing Catalyst A with H₂ at about 500° C.for about 1 hour.

Catalyst C was prepared by multiple impregnations of about 1 gram ofCatalyst A (unreduced) with 2.5 grams of concentrated HNO₃ at roomtemperature and drying at 125° C. after each acid impregnation step,followed by calcining in air at about 400° C. for about 3 hours, and afinal reduction step with H₂ at about 500° C. for about 1 hour.

Catalyst D was prepared by subjecting Catalyst A to multiple reducingtreatments with H₂ at 500° C. (for a total time of about 2.5 hours),followed by multiple acid treatments with 2.5 grams of concentratedHNO₃, drying between each acid impregnation, calcination in air at 400°C. for about 3 hours, and reduction with H₂ at about 500° C. for about 1hour.

Catalysts B, C and D were tested for CO oxidation activity. A gaseousfeed comprising 1.2 volume percent CO, 0.6 volume percent O₂, 32 volumepercent CO₂, 32 volume percent He and N₂ as the remainder was passedthrough a needle valve and a glass reactor tube of 6 mm inner diameterin an upflow direction. The glass reactor contained 1.0 gram of CatalystB or C or D in a bed of about 2 cm height. The temperature in thecatalyst bed was measured by means of a thermocouple inserted into thetop layer of the catalyst bed. The CO content of the reactor effluentwas determined by means of a Series 400 Anarad IR analyzer.

All tests were carried out at ambient conditions (about 25°-30° C., 1atm.) and a flow rate of the feed gas of 400 cc per minute per gramcatalyst. Test results are summarized in Table I.

                  TABLE I                                                         ______________________________________                                                Cubic Centimeter                                                      Hours   CO Converted Per Minute Per Gram Catalyst                             on Stream                                                                             Catalyst B   Catalyst C    Catalyst D                                 ______________________________________                                          0.5   1.58         2.63          --                                         1       1.22         2.29          --                                         2       0.99         1.95          --                                         3       0.81         1.80          --                                         4       0.72                                                                          re-reduced w. H.sub.2                                                                      re-reduced w. H.sub.2                                            at 500° C., 0.5 hr.                                                                 at 500° C., 0.75 hr.                                0.5   2.78         3.23          2.67                                       1       2.34         2.72          2.61                                       2       1.99         2.28          2.61                                       3       1.80         2.04          2.62                                       4       1.64         1.89          2.61                                       5       1.51         1.78          2.58                                       6       1.38         1.68          2.55                                       8       1.18         1.49          2.48                                       10      1.04         1.31          2.41                                       12      0.91         1.18          2.32                                       14      0.83         1.08          2.29                                       16      --           1.07          2.27                                       ______________________________________                                         NOTE:                                                                         Percent CO conversion data can be calculated by multiplying the data in       Table I (i.e., cc CO/minute/gram) by a factor of about 20.8.             

Test data in Table I clearly show that Catalyst D (acid-treated afterreduction) lost only about 14% of its initial activity during a 14-hourtime period, whereas the relative activity decrease of control CatalystsB and C was 70% and 67%, respectively, during the same time period.Thus, the catalyst which was prepared in accordance with the method ofthis invention exhibited a much higher catalyst life and will be moresuitable in extended applications, e.g., in CO₂ -filled lasers and thelike, than catalysts which had not been acid-treated (Catalyst B) or wasacid-treated before the first reduction step (Catalyst C).

EXAMPLE II

This example provides additional test results on the effect of acidtreatment of reduced Pt/Fe/Al₂ O₃ catalysts on CO oxidation activity.

Commercial alumina spheres (1/8-inch diameter; not containing Pt;provided by Aluminum Company of America, Pittsburg, Pa.) wereimpregnated with dissolved compounds of Pt and Fe, dried and calcined,substantially in accordance with the procedure described in Example I.This material, labeled Catalyst E, contained 3 weight percent Pt and 1.5weight percent Fe (as iron oxide).

Catalyst F was prepared by heating Catalyst E in hydrogen gas at 300° C.for 3 hours.

Catalyst G was prepared by impregnating Catalyst F using nitric acid,drying, calcining in air, and heating again in hydrogen gas at 300° C.for 3 hours, substantially as described in Example I.

Both catalysts were tested in accordance with the CO oxidation proceduredescribed in Example I. The CO conversion attained with Catalyst Fdecreased from about 89% (4.3 cc CO/minute/g catalyst) after 1 hour onstream to about 43% (2.1 cc CO/minute/g catalyst) after 18 hours onstream, whereas the CO conversion attained with Catalyst G decreasedfrom about 96% (4.6 cc CO/minute/g catalyst) after 1 hour on stream toabout 53% (2.5 cc CO/minute/g catalyst) after 18 hours on stream. Thesetest results demonstrate the superiority of invention Catalyst G.

In another test series, alumina spheres (1/8 inch diameter) wereimpregnated with dissolved compounds of Pt and Fe, dried and calcined,substantially as described above. This material, labeled Catalyst H,contained 2 weight percent Pt and 1 weight percent Fe (as iron oxide).

Catalyst I was prepared by reducing Catalyst H with H₂ gas at 300° C.for 3 hours, followed by soaking twice with glacial acetic acid, drying,calcining, and reducing in H₂ gas, as described above.

The CO conversion attained with Catalyst I in a CO oxidation test, inaccordance with the procedure of Example I, was about 90% (4.3 ccCO/minute/g catalyst) after 1 hour on stream, and about 57% (2.7 ccCO/minute/g catalyst) after about 22 hours on stream. This exampleillustrates that acids other than nitric acid can be used in preparingthe CO oxidation catalyst of the invention.

EXAMPLE III

This example illustrates the preparation of magnesium aluminatesupported Pt/Fe catalysts and their performance in low temperature COoxidation tests.

5/8-inch magnesium aluminate rings (provided by Haldor-Topsoe, Inc.;Houston, Tex.) were impregnated with compounds of Pt and Fe (by multipleimpregnations and drying steps between impregnations), dried andcalcined, substantially in accordance with the procedure described inExample I. This calcined material, labeled Catalyst J, contained 3.0weight percent Pt and 1.5 weight percent Fe (as iron oxide).

Catalyst K was prepared by reducing Catalyst J with H₂ gas at 300° C.for 3 hours.

Catalyst L was prepared by impregnating Catalyst K with nitric acid,drying, calcining and re-reducing (at 300° C./3 hours), substantially inaccordance with the procedure of Example I.

Catalysts K and L were tested in a CO oxidation test, in accordance withthe procedure described in Example I. The CO conversion attained withCatalyst K was about 43% (1.0 cc CO/minute/g catalyst) after 1 hour onstream, and about 25% (0.6 cc CO/g catalyst/minute) after 22 hours onstream. The CO conversion attained with invention Catalyst L was about61% (1.4 cc CO/minute/g catalyst) after 1 hour on stream, and about 39%(0.9 cc CO/minute/g catalyst) after 22 hours on stream. These testresults clearly demonstrate the superiority of the Mg aluminatesupported catalyst which had been prepared in accordance with the methodof this invention (comprising acid treatment after reduction).

Reasonable variations, modifications and adaptations for variousconditions and uses can be made within the scope of the disclosure andappended claims.

That which is claimed is:
 1. In a process for oxidizing carbon monoxidewith free oxygen to a carbon dioxide in the presence of a catalystcomposition comprising (a) a support material selected from the groupconsisting of alumina, magnesium aluminate and mixtures thereof, (b)platinum metal, and (c) an iron component selected from the groupconsisting of iron oxide, iron metal and mixtures thereof, wherein saidcatalyst composition has undergone a reducing treatment, the improvementwhich comprises:(1) treating said catalyst composition, which hasundergone a reducing treatment, with an acidic liquid; (2) heating thematerial obtained in step (1) under such conditions as to substantiallyremove said acidic liquid from said material obtained in step (1); and(3) treating the material obtained in step (2) with a reducing gas undersuch conditions as to enhance the activity of said material forcatalyzing the reaction of carbon monoxide with free oxygen to carbondioxide.
 2. A process in accordance with claim 1, wherein said supportmaterial is alumina.
 3. A process in accordance with claim 2, whereinsaid catalyst composition comprises about 0.1 to about 10 weight-% Ptand about 0.05 to about 20 weight-% Fe.
 4. A process in accordance withclaim 1, wherein said support material is magnesium aluminate.
 5. Aprocess in accordance with claim 4, wherein said catalyst compositioncomprises about 0.1 to about 10 weight-% Pt and about 0.05 to about 20weight-% Fe.
 6. A process in accordance with claim 1, wherein saidsupport material is a mixture of alumina and magnesium aluminate.
 7. Aprocess in accordance with claim 6, wherein said catalyst compositioncomprises about 0.1 to about 10 weight-% Pt and about 0.05 to about 20weight-% Fe.
 8. A process in accordance with claim 1, wherein said ironcomponent consists essentially of iron oxide.
 9. A process in accordancewith claim 1, wherein said catalyst composition consists essentially ofcomponents (a), (b) and (c).
 10. A process in accordance with claim 1,wherein said acidic liquid used in step (1) is selected from the groupconsisting of aqueous solutions of acetic acid and glacial acetic acid.11. A process in accordance with claim 1, wherein step (1) is carriedout at about 10°-80° C. for about 0.01-1 hour.
 12. A process inaccordance with claim 1, wherein step (2) is carried out at atemperature in the range of from about 80° to about 700° C.
 13. Aprocess in accordance with claim 12, wherein step (2) is carried out intwo sub-steps: first substantially drying the material obtained in step(1) at a temperature of about 80°-200° C. for about 0.3-10 hours, andthereafter heating the substantially dried material at about 250°-700°C. for about 0.2-10 hours.
 14. A process in accordance with claim 1,wherein said reducing gas used in step (3) is hydrogen.
 15. A process inaccordance with claim 14, wherein step (3) is carried out at about20°-650° C. for about 0.5-20 hours.
 16. A process in accordance withclaim 1, wherein said process for oxidizing carbon monoxide is carriedout at a temperature in the range of from about -50° to about 400° C.17. A process in accordance with claim 16, wherein said temperature isabout 10°-50° C.
 18. A process in accordance with claim 16, wherein saidprocess for oxidizing carbon monoxide is carried out at a volume ratioof CO to O₂ of about 1:100 to about 100:1 and a pressure of about0.1-2,000 psia.
 19. A process in accordance with claim 1, wherein saidprocess for oxidizing carbon monoxide is carried out in a cavity of acarbon dioxide laser.
 20. A process in accordance with claim 1, whereinsaid acidic liquid used in step (1) is an aqueous solution of nitricacid.